Analysis Of Optical Coherence Tomography Data Research Articles

Differential Study of Retinal Thicknesses in the Eyes of Alzheimer's Patients, Multiple Sclerosis Patients and Healthy Subjects.

Multiple sclerosis (MS) and Alzheimer's disease (AD) cause retinal thinning that is detectable in vivo using optical coherence tomography (OCT). To date, no papers have compared the two diseases in terms of the structural differences they produce in the retina. The purpose of this study is to analyse and compare the neuroretinal structure in MS patients, AD patients and healthy subjects using OCT. Spectral domain OCT was performed on 21 AD patients, 33 MS patients and 19 control subjects using the Posterior Pole protocol. The area under the receiver operating characteristic (AUROC) curve was used to analyse the differences between the cohorts in nine regions of the retinal nerve fibre layer (RNFL), ganglion cell layer (GCL), inner plexiform layer (IPL) and outer nuclear layer (ONL). The main differences between MS and AD are found in the ONL, in practically all the regions analysed (AUROCFOVEAL = 0.80, AUROCPARAFOVEAL = 0.85, AUROCPERIFOVEAL = 0.80, AUROC_PMB = 0.77, AUROCPARAMACULAR = 0.85, AUROCINFERO_NASAL = 0.75, AUROCINFERO_TEMPORAL = 0.83), and in the paramacular zone (AUROCPARAMACULAR = 0.75) and infero-temporal quadrant (AUROCINFERO_TEMPORAL = 0.80) of the GCL. In conclusion, our findings suggest that OCT data analysis could facilitate the differential diagnosis of MS and AD.

The Use of Optical Coherence Tomography for Early Glaucoma Screening in a Population of Patients with Diabetes

ABSTRACT Purpose The utility of screening for early diagnosis of glaucoma remains a widely debated topic in the care of ophthalmic patients. There are currently no population-based guidelines regarding screening for glaucoma. The purpose of this study is to determine the utility of optical coherence tomography (OCT) for early glaucoma screening in a population of diabetic patients. The results of this study may inform future screening practices. Methods The current study is a post hoc analysis of OCT data collected from diabetic patients screened for eye disease over 6 months. Glaucoma suspects (GS) were identified based on abnormal retinal nerve fiber layer (RNFL) thickness on OCT. Fundus photographs of GS were graded by two independent raters for vertical cup-to-disc ratio (CDR) and other signs of glaucomatous changes. Results Of the 807 subjects screened, 50 patients (6.2%) were identified as GS. The mean RNFL thickness for GS was significantly lower than the mean RNFL in the total screening population (p < .001). Median CDR for GS was 0.44. Twenty-eight eyes of 17 GS were marked as having optic disc notching or rim thinning by at least one grader. Cohen’s kappa statistic for inter-rater reliability was 0.85. Racial differences showed that mean CDR was significantly higher in non-whites (p < .001). Older age was associated with thinner RNFL (r = −0.29, p = .004). Conclusions Results of this study suggest that in a sample of diabetic patients, a small but clinically significant minority may be flagged as GS based on OCT. Nearly one-third of GS eyes were found to have glaucomatous changes on fundus photography by at least one grader. These results suggest screening with OCT may be useful in detecting early glaucomatous changes in high-risk populations, particularly older, non-white patients with diabetes.

Данные о распределении патологической ретинальной жидкости у пациентов с неоваскулярной возрастной макулярной дегенерацией, получавших антиангиогенную терапию в течение 5 лет в условиях реальной клинической практики

Purpose. To analyze the distribution of pathological retinal fluids according to optical coherence tomography (OCT) over time in patients with neovascular age-related macular degeneration (nAMD) who received anti-angiogenic therapy for 5 years. Material and methods. A retrospective analysis of OCT data of patients treated with anti-VEGF therapy (ranibizumab, aflibercept) in the 3+PRN regimen was performed. The study group consisted of 24 patients (79.2 % women, mean age 70.5 years). Results. Best corrected visual acuity increased from the initial 0.31 0.42 0.52 to 0.40 0.50 0.60 (p = 0.00028) by the 60th month. Central retinal thickness decreased from initial 304.0 343.4 382.7 µm to 190.6 209.8 229.1 µm (p &lt; 0.00001). Significant correlation indicators according to Spearman (p &lt; 0.05) were established in relation to an increase in the proportion of patients who had a «dry» retina and cases of subretinal fluid (SRF) resolution. Using the method of proportions, a significant (p &lt; 0.05) increase in the proportion of patients without pathological fluid was determined, as well as a decrease in the percentage of patients with SRF and sub-retinal pigment epithelium fluid, which were achieved in the first year of therapy and maintained until the end of the study, as well as a decrease in the proportion of patients with intraretinal fluid, which achieved a statistical significance (p &lt; 0.05) by the 60th month. Conclusion. One of the indicators confirming the high efficiency of long-term (60 months) anti-VEGF therapy for nAMD was a decrease in the proportion of patients with all compartments of the pathological retinal fluid. Keywords: age-related macular degeneration, anti-VEGF therapy, optical coherence tomography, retinal fluid, biomarkers

A Deep Ensemble Learning-Based CNN Architecture for Multiclass Retinal Fluid Segmentation in OCT Images

Retinal Fluids (fluid collections) develop because of the accumulation of fluid in the retina, which may be caused by several retinal disorders, and can lead to loss of vision. Optical coherence tomography (OCT) provides non-invasive cross-sectional images of the retina and enables the visualization of different retinal abnormalities. The identification and segmentation of retinal cysts from OCT scans is gaining immense attention since the manual analysis of OCT data is time consuming and requires an experienced ophthalmologist. Identification and categorization of the retinal cysts aids in establishing the pathophysiology of various retinal diseases, such as macular edema, diabetic macular edema, and age-related macular degeneration. Hence, an automatic algorithm for the segmentation and detection of retinal cysts would be of great value to the ophthalmologists. In this study, we have proposed a convolutional neural network-based deep ensemble architecture that can segment the three different types of retinal cysts from the retinal OCT images. The quantitative and qualitative performance of the model was evaluated using the publicly available RETOUCH challenge dataset. The proposed model outperformed the state-of-the-art methods, with an overall improvement of 1.8%.

Synthetic OCT Data Generation to Enhance the Performance of Diagnostic Models for Neurodegenerative Diseases.

PurposeOptical coherence tomography (OCT) has recently emerged as a source for powerful biomarkers in neurodegenerative diseases such as multiple sclerosis (MS) and neuromyelitis optica (NMO). The application of machine learning techniques to the analysis of OCT data has enabled automatic extraction of information with potential to aid the timely diagnosis of neurodegenerative diseases. These algorithms require large amounts of labeled data, but few such OCT data sets are available now.MethodsTo address this challenge, here we propose a synthetic data generation method yielding a tailored augmentation of three-dimensional (3D) OCT data and preserving differences between control and disease data. A 3D active shape model is used to produce synthetic retinal layer boundaries, simulating data from healthy controls (HCs) as well as from patients with MS or NMO.ResultsTo evaluate the generated data, retinal thickness maps are extracted and evaluated under a broad range of quality metrics. The results show that the proposed model can generate realistic-appearing synthetic maps. Quantitatively, the image histograms of the synthetic thickness maps agree with the real thickness maps, and the cross-correlations between synthetic and real maps are also high. Finally, we use the generated data as an augmentation technique to train stronger diagnostic models than those using only the real data.ConclusionsThis approach provides valuable data augmentation, which can help overcome key bottlenecks of limited data.Translational RelevanceBy addressing the challenge posed by limited data, the proposed method helps apply machine learning methods to diagnose neurodegenerative diseases from retinal imaging.

Послеоперационная деформация ИОЛ, методика выявления и влияние на послеоперационную рефракцию

Purpose. To determine IOL deformation in patients after phacoemulsification using optical coherence tomography (OCT) and to identify associated shift of postoperative refraction. Results. A "deflection" along the axis was detected during the OCT data analysis. In 38 cases (17.27 %) the center of the optical part of the lens was shifted toward the retina. The amplitude of this shift was 8.41 ± 8.28 mkm (from 0.00 to 30.00 mkm). At the same time patients with the "deflection" of the optical part of the IOL have large values of axial length (AL) accompanied with a great corneal segment diameter size, a deeper anterior chamber of the pseudophakic eye and its larger volume after IOL implantation. The obtained subjective refraction and the autorefractometry data in the form of a spherical equivalent were compared with the expected value of the calculated refraction using standard formulas. The average amplitude of the refraction shift was 0.25 diopters towards hypermetropia. Mathematical models based of logistic regression were constructed to predict the probability of the lens "deflection". The model based on only IOL power value (AUROC = 0.89 ± 0.07) stood out with good predictive quality and the possibility of interpretation. A high probability of IOL "deflection" was revealed when its power was not greater than ≥ 18.5 diopters. Another models was built based on sets of biometry data measured with Lenstar LS900: the axial length and anterior chamber depth of of the phakic eye, the diameter of the corneal segment and the average keratometry data calculated within the main meridians. This one have also high predictive quality: AUROC = 0.93 ± 0.06. Conclusion. Based on the data of optical coherence tomography, it is possible to detect the axial "deflection" of the optical part of the intraocular lens. The deflection of the IOL is reflected in the hypermetropia refractive shift relative to that calculated by the formulas of Hoffer Q, Holladay I and Haigis, which requires correction. To calculate the probability of displacement of the implanted IOL towards the retina, 2 logistic regression models with good predictive quality and the possibility of interpretation for the have been developed. Keywords: cataract, "deflection" along the axis, phacoemulsification, IOL deformation, optical coherence tomography

Circular functional analysis of OCT data for precise identification of structural phenotypes in the eye

Progressive optic neuropathies such as glaucoma are major causes of blindness globally. Multiple sources of subjectivity and analytical challenges are often encountered by clinicians in the process of early diagnosis and clinical management of these diseases. In glaucoma, the structural damage is often characterized by neuroretinal rim (NRR) thinning of the optic nerve head, and other clinical parameters. Baseline structural heterogeneity in the eyes can play a key role in the progression of optic neuropathies, and present challenges to clinical decision-making. We generated a dataset of Optical Coherence Tomography (OCT) based high-resolution circular measurements on NRR phenotypes, along with other clinical covariates, of 3973 healthy eyes as part of an established clinical cohort of Asian Indian participants. We introduced CIFU, a new computational pipeline for CIrcular FUnctional data modeling and analysis. We demonstrated CIFU by unsupervised circular functional clustering of the OCT NRR data, followed by meta-clustering to characterize the clusters using clinical covariates, and presented a circular visualization of the results. Upon stratification by age, we identified a healthy NRR phenotype cluster in the age group 40–49 years with predictive potential for glaucoma. Our dataset also addresses the disparity of representation of this particular population in normative OCT databases.

Segmentation of anterior segment boundaries in swept source OCT images

Quantification of the eye’s anterior segment morphology from optical coherence tomography (OCT) images is crucial for research and clinical decision-making, including the diagnosis and monitoring of many ocular diseases. Structural parameters, such as tissue thickness and area are the most common metrics used to quantify these medical images, and tissue segmentation is required before these metrics can be extracted. Currently, swept source OCT allows the capture of cross-sectional images that encompass the entire anterior segment with a high level of detail. However, the manual annotation of tissue boundaries is time-consuming. In this work, an algorithm based on graph-search theory combined with boundary-specific image transformation is applied for the segmentation of anterior segment OCT images. We demonstrate that the method can reliably segment 5 different tissue boundaries in healthy eyes with low boundary error (mean error below 1 pixel across all boundaries). The technique can be used to extract clinically relevant parameters such as central corneal and crystalline lens thickness as well as anterior chamber depth and area, with a high level of agreement with manual segmentation (normalized errors below 1.6%). The proposed method provides a tool that can support clinical and research OCT data analysis.

Thickness of Intraretinal Layers in Patients with Type 2 Diabetes Mellitus Depending on a Concomitant Diabetic Neuropathy: Results of a Cross-Sectional Study Using Deviation Maps for OCT Data Analysis

Optical coherence tomography (OCT) supports the detection of thickness changes in intraretinal layers at an early stage of diabetes mellitus. However, the analysis of OCT data in cross-sectional studies is complex and time-consuming. We introduce an enhanced deviation map-based analysis (MA) and demonstrate its effectiveness in detecting early changes in intraretinal layer thickness in adults with type 2 diabetes mellitus (T2DM) compared to common early treatment diabetic retinopathy study (ETDRS) grid-based analysis (GA). To this end, we obtained OCT scans of unilateral eyes from 33 T2DM patients without diabetic retinopathy and 40 healthy controls. The patients were categorized according to concomitant diabetic peripheral neuropathy (DN). The results of MA and GA demonstrated statistically significant differences in retinal thickness between patients and controls. Thinning was most pronounced in total retinal thickness and the thickness of the inner retinal layers in areas of the inner macular ring, selectively extending into areas of the outer macular ring and foveal center. Patients with clinically proven DN showed the strongest thinning of the inner retinal layers. MA showed additional areas of thinning whereas GA tended to underestimate thickness changes, especially in areas with localized thinning. We conclude that MA enables a precise analysis of retinal thickness data and contributes to the understanding of localized changes in intraretinal layers in adults with T2DM.

Spatial coordinate corrected motion tracking for optical coherence elastography.

We develop a spatial coordinate corrected (SCC) motion tracking method for optical coherence elastography. SCC motion tracking refers the instantaneous velocity field extracted from optical coherence tomography (OCT) data to the laboratory coordinate system and accurately reconstructs the displacement field established during the mechanical excitation (compression) process. We acquired image data from compression OCE experiments on human breast tissue specimens, and reconstructed the displacement field through Doppler analysis of OCT data. Our results suggested that SCC tracking enables accurate reconstruction of displacement field, and enables effective identification mechanical heterogeneity that can be used as a biomarker for cancer diagnosis and tumor margin assessment.

Algorithm for predicting axial displacement of the optic part of IOL after phacoemulsification

To test a prediction algorithm for deflection of the optical part of IOL after uncomplicated phacoemulsification. The study included 226 patients (287 eyes) who underwent phacoemulsification with implantation of intracapsular AcrySof IOL. Preoperative examination included IOLMaster, Lenstar LS 900 biometry and Pentacam HR keratotopography. All measurement were repeated one month postoperatively. To determine the tilt and deflection of the IOL's optical part, anterior segment optical coherence tomography (OCT) was performed on Topcon 3DOCT-2000. OCT data analysis helps identify the slope and deflection of the IOL's optical part relative to the pupil plane. In the previous study we built logistic regression models for predicting the deflection of the IOL's optical part with high predictive quality based on the calculated IOL power and preoperative biometry measurements. When checked with new patient data, the areas under the ROC curves have changed slightly. Large area under the ROC curves with small deviation rates, as well as retention of the level of true positive responses with little increase in false negative responses verify the high quality of the models. Logistic regression models based on the optical power of the implanted IOL, as well as on a combination of preoperative biometry data from IOLMaster and Lenstar LS 900, make it possible to predict the probability of deflection of the optical part of IOL with high reliability and promptly correct the IOL power.

Dynamic programming and automated segmentation of optical coherence tomography images of the neonatal subglottis: enabling efficient diagnostics to manage subglottic stenosis.

.Subglottic stenosis (SGS) is a challenging disease to diagnose in neonates. Long-range optical coherence tomography (OCT) is an optical imaging modality that has been described to image the subglottis in intubated neonates. A major challenge associated with OCT imaging is the lack of an automated method for image analysis and micrometry of large volumes of data that are acquired with each airway scan (1 to 2 Gb). We developed a tissue segmentation algorithm that identifies, measures, and conducts image analysis on tissue layers within the mucosa and submucosa and compared these automated tissue measurements with manual tracings. We noted small but statistically significant differences in thickness measurements of the mucosa and submucosa layers in the larynx (), subglottis (), and trachea (). The automated algorithm was also shown to be over 8 times faster than the manual approach. Moderate Pearson correlations were found between different tissue texture parameters and the patient’s gestational age at birth, age in days, duration of intubation, and differences with age (mean age 17 days). Automated OCT data analysis is necessary in the diagnosis and monitoring of SGS, as it can provide vital information about the airway in real time and aid clinicians in making management decisions for intubated neonates.

Deviation Maps for Understanding Thickness Changes of Inner Retinal Layers in Children with Type 1 Diabetes Mellitus

ABSTRACTPurpose: To analyze the use of deviation maps (DevMs) to understand thickness changes of inner retinal layers in optical coherence tomography (OCT) data. To test a new visual analytics (VA) method with reduced complexity of OCT data analysis by comparing the layer thickness of children with type 1 diabetes mellitus (T1DM) to matched controls.Methods: OCT was performed on unilateral eyes of 26 children with T1DM without diabetic retinopathy and 29 healthy children to obtain macular volume scans. Subsequently, segmented inner retinal layers were analyzed using VA. Deviation maps were generated to readily visualize thickness differences between both groups and to investigate thickness changes of individual patients in relation to the control group.Results: In DevMs of the patient group, the total retina (TR) demonstrated localized, irregular areas of thinning (mean ± standard deviation) involving foveal center, inner macula, and inferior-nasal outer macula (−9.31 ± 1.73 µm; p < 0.05). Similarly, retinal nerve fiber layer showed continuous and localized areas of thinning in both inner and outer macula, extending nasally (−5.45 ± 4.31 µm; p < 0.05). In DevMs of individual patients, the TR and inner retinal layers revealed remarkable changes in thickness that were present between patients at both late and early stages of diabetes.Conclusion: The VA method simplifies the in-depth analysis of OCT volume data from different groups and is effective in detecting retinal thickness changes in children with diabetes. It can be easily adopted in a clinical set-up and intuitively used in complex multidisciplinary studies.

Accurate Monte Carlo simulation of frequency-domain optical coherence tomography.

Optical coherence tomography (OCT) relies on optical interferometry to provide noninvasive imaging of living tissues. In addition to its 3D imaging capacity for medical diagnosis, its potential use for recovering optical parameters of biological tissues for biological and pathological analyses has also been explored by researchers, as pathological changes in tissue alter the microstructure of the tissue and therefore its optical properties. We aim to develop a new approach to OCT data analysis by estimating optical properties of tissues from OCT scans, which are invisible in the scans. This is an inverse problem. Solving an inverse problem involves a forward modeling step to simulate OCT scans of the tissues with hypothesized optical parameter values and an inverse step to estimate the real optical par1meters values by matching the simulated scans to real scans. In this paper, we present a Monte Carlo (MC)–based approach for simulating the frequency‐domain OCT. We incorporated a focusing Gaussian light beam rather than an infinitesimally thin light beam for accurate simulations. A new and more accurate photon detection scheme is also implemented. We compare our MC model to an analytical OCT model based on the extended Huygens‐Fresnel principle (EHF) to demonstrate the consistency between the two models. We show that the two models are in good agreement for tissues with high scattering and high anisotropy factors.

Amiloride does not protect retinal nerve fibre layer thickness in optic neuritis in a phase 2 randomised controlled trial

Background: Recent basic and clinical evidence suggests amiloride may be neuroprotective in multiple sclerosis (MS) through the blockade of the acid sensing ion channel (ASIC). Objective: To examine the neuroprotective efficacy of amiloride in acute optic neuritis (ON). Methods: A total of 48 patients were recruited to a phase 2, double blind, single site, randomised controlled trial. Scanning laser polarimetry (GDx) at 6 months was the primary outcome measure and optical coherence tomography (OCT) and visual and electrophysiological measures were secondary outcome measures. Participants aged 18–55 years, ≤28 days of onset of first episode unilateral ON, were randomised to amiloride (10 mg daily for 5 months) or placebo (clinicaltrials.gov, NCT 01802489). Results: Intention-to-treat (ITT) cohort consisted of 43 patients; 23 placebo and 20 amiloride. No significant drug-related adverse events occurred. No significant differences were found in GDx (p = 0.840). Visual evoked potentials (VEP) were significantly prolonged in the amiloride group compared to placebo (p = 0.004). All other secondary outcome measures showed no significant difference. Baseline analysis of OCT data demonstrated a significant pre-randomisation thinning of ganglion cell layer. Conclusion: Amiloride has not demonstrated any neuroprotective benefit within this trial paradigm, but future neuroprotective trials in ON should target the window of opportunity to maximise potential neuroprotective benefit.

Prostate cancer diagnosis: the feasibility of needle-based optical coherence tomography.

The objective of this study is to demonstrate the feasibility of needle-based optical coherence tomography (OCT) and functional analysis of OCT data along the full pullback trajectory of the OCT measurement in the prostate, correlated with pathology. OCT images were recorded using a commercially available C7-XR™ OCT Intravascular Imaging System interfaced to a C7 Dragonfly™ intravascular 0.9-mm-diameter imaging probe. A computer program was constructed for automated image attenuation analysis. First, calibration of the OCT system for both the point spread function and the system roll-off was achieved by measurement of the OCT signal attenuation from an extremely weakly scattering medium (Intralipid® 0.0005 volume%). Second, the data were arranged in 31 radial wedges (pie slices) per circular segments consisting of 16 A-scans per wedge and 5 axial B-scans, resulting in an average A-scan per wedge. Third, the decay of the OCT signal is analyzed over 50 pixels ([Formula: see text]) in depth, starting from the first found maximum data point. Fourth, for visualization, the data were grouped with a corresponding color representing a specific [Formula: see text] range according to their attenuation coefficient. Finally, the analyses were compared to histopathology. To ensure that each single use sterile imaging probe is comparable to the measurements of the other imaging probes, the probe-to-probe variations were analyzed by measuring attenuation coefficients of 0.03, 6.5, 11.4, 17, and 22.7 volume% Intralipid®. Experiments were repeated five times per probe for four probes. Inter- and intraprobe variation in the measured attenuation of Intralipid samples with scattering properties similar to that of the prostate was [Formula: see text] of the mean values. Mean attenuation coefficients in the prostate were [Formula: see text] for parts of the tissue that were classified as benign (SD: [Formula: see text], minimum: [Formula: see text], maximum: [Formula: see text]) and [Formula: see text] for parts of tissue that were classified as malignant (SD: [Formula: see text], minimum: [Formula: see text], maximum: [Formula: see text]). In benign areas, the tissue looked homogeneous, whereas in malignant areas, small glandular structures were seen. However, not all areas in which a high attenuation coefficient became apparent corresponded to areas of prostate cancer. This paper describes the first in-tissue needle-based OCT imaging and three-dimensional optical attenuation analysis of prostate tissue that indicates a correlation with pathology. Fully automated attenuation coefficient analysis was performed at 1300nm over the full pullback. Correlation with pathology was achieved by coregistration of three-dimensional (3-D) OCT attenuation maps with 3-D pathology of the prostate. This may contribute to the current challenge of prostate imaging and the rising interest in focal therapy for reduction of side effects occurring with current therapies.

Quantitative characterization of developing collagen gels using optical coherence tomography

Nondestructive optical imaging methods such as optical coherence tomography (OCT) have been proposed for characterizing engineered tissues such as collagen gels. In our study, OCT was used to image collagen gels with different seeding densities of smooth muscle cells (SMCs), including acellular gels, over a five-day period during which the gels contracted and became turbid with increased optical scattering. The gels were characterized quantitatively by their optical properties, specified by analysis of OCT data using a theoretical model. At 6 h, seeded cell density and scattering coefficient (mu(s)) were correlated, with mu(s) equal to 10.8 cm(-1)(10(6) cells mL). Seeded cell density and the scattering anisotropy (g) were uncorrelated. Over five days, the reflectivity in SMC gels gradually doubled with little change in optical attenuation, which indicated a decrease in g that increased backscatter, but only a small drop in mu(s). At five days, a subpopulation of sites on the gel showed substantially higher reflectivity (approximately a tenfold increase from the first 24 h). In summary, the increased turbidity of SMC gels that develops over time is due to a change in the structure of collagen, which affects g, and not simply due to a change in number density of collagen fibers due to contraction.

10th Annual Congress of the German Association of Clinical Pharmacology

10th Annual Congress of the German Association of Clinical Pharmacology

Optical Coherence Tomography Measurements and Analysis Methods in Optical Coherence Tomography Studies of Diabetic Macular Edema

To evaluate optical coherence tomography (OCT) measurements and methods of analysis of OCT data in studies of diabetic macular edema (DME). Associations of pairs of OCT variables and results of 3 analysis methods using data from 2 studies of DME. Two hundred sixty-three subjects from a study of modified Early Treatment of Diabetic Retinopathy Study (mETDRS) versus modified macular grid (MMG) photocoagulation for DME and 96 subjects from a study of diurnal variation of DME. Correlations were calculated for pairs of OCT variables at baseline and for changes in the variables over time. Distribution of OCT measurement changes, predictive factors for OCT measurement changes, and treatment group outcomes were compared when 3 measures of change in macular thickness were analyzed: absolute change in retinal thickness, relative change in retinal thickness, and relative change in retinal thickening. Concordance of results using different OCT variables and analysis methods. Center point thickness correlated highly with central subfield mean thickness (CSMT) at baseline (0.98-0.99). The distributions of changes in CSMT were approximately normally distributed for absolute change in retinal thickness and relative change in retinal thickness, but not for relative change in retinal thickening. Macular thinning in the mETDRS group was significantly greater than in the MMG group when absolute change in retinal thickness was used, but not when relative change in thickness and relative change in thickening were used. Relative change in macular thickening provides unstable data in eyes with mild degrees of baseline thickening, unlike the situation with absolute or relative change in retinal thickness. Central subfield mean thickness is the preferred OCT measurement for the central macula because of its higher reproducibility and correlation with other measurements of the central macula. Total macular volume may be preferred when the central macula is less important. Absolute change in retinal thickness is the preferred analysis method in studies involving eyes with mild macular thickening. Relative change in thickening may be preferable when retinal thickening is more severe.

Intraobserver variability in optical coherence tomography

Purpose To assess the intraobserver variability of optical coherence tomography (OCT) in patients with clinically stable maculas. Design Retrospective, observational case series using a diagnostic instrument. Methods Retrospective study. setting. Private retina practice. patient population. Twenty-two eyes of 19 patients, each studied twice within 4 months. observation procedure. Optical coherence tomograph measurements of the macula obtained by two photographers. main outcome measures. Ordinary least products (OLP) and Bland-Altman analysis of OCT data. Results No fixed or proportional bias was detected in foveal zone thickness and total macular volume between measurements of either of the OCT operators. The coefficient of repeatability for foveal zone thickness was 37.0 μm for photographer 1 and 34.8 μm for photographer 2. The coefficient of repeatability for total macular volume was 0.29 mm 3 for photographer 1 and 0.10 mm 3 for photographer 2. Conclusion Foveal zone thickness and total macular volume measurements show low intraobserver variability when analyzed by OLP and Bland-Altman techniques. Bounds are given for foveal zone thickness and total macular volume for which longitudinal OCT measurements by the same operator can be considered to reflect natural history or intervention effects rather than intraobserver variability.